Bone Dragon does not return with reinforcements. [Fixed in 2.9]

Enygma6

I had Bone Dragon on the battlefield and reinforced 1x time.  
Playing using Liliana, Untouched by Death, and I had used her 1st ability a couple times during the match to ensure there were sufficient cards in the graveyard.  
On my final turn, I used Murder on my own Bone Dragon to test out the self-resurrection functionality.  
The dragon did return to the battlefield, but without any reinforcements.  I can understand it not getting any of the additional discarded copies of Bone Dragon as reinforcements, but it should have at least had the 1x, from the two copies that had been cast from hand.

//Edited Title -Brigby

Enygma6

More to add to the Bone Dragon failures, this time in a Training Grounds match:  
Using Liliana, Untouched by Death (level 60), I had used her 1st ability "Fill the Graves" 3 times before my Bone Dragon was killed by my opponent.  It did not regenerate.  
I was able to bring it back with Dark Petition.  
Later my opponent killed it again, but by then I had used "Fill the Graves" another 1 or 2 times, and the Bone Dragon was returned to the battlefield as expected.  
Never once did I see my opponent (level 60 Nicol Bolas, God-Pharaoh) cast or do anything that would have affected my graveyard.

Either Bone Dragon requires 25+ cards in the graveyard, or Liliana, Untouched by Death's 1st ability is not putting 8 cards into the graveyard.

Enygma6

Further testing shows that Liliana is capable of putting 8 cards into her graveyard with Fill the Graves.  
A deck of 8 zombie creatures and 2 loyalty generators was used, and I was able to deal between 4 and 8 damage per activation of her 1st ability.

So the problem is specifically to Bone Dragon's checking the graveyard status.
In the previous incident when it did not regenerate, the dragon was not disabled.  It was the beginning of my opponent's turn, and they used Nicol Bolas's 1st ability to do a direct kill on my creature.  
The second kill (from which it regenerated) was inflicted by my opponent casting Tetzimoc and its -6/-6 ETB effect.  
  
A direct-kill from Murder did trigger the Bone Dragon regeneration in the incident in the 1st post above.  
Unless there is some difference between the two "kill creature" functions in the code, I do not see why this would happen.  

Every new set release seems to default back to the original "kill by inflicting max damage" function, which always causes problems with creatures that have Prevent Damage.  
There is a separate kill function that bypasses Prevent Damage, and it seems cards have to be updated for this on a case-by-case basis.  
The cards in M19 that do a direct kill (Murder, Transmogrifying Wand, etc) have yet to be updated, and still appear to do an 'inflict max damage' effect.  Further testing with proper kill cards will be tried next.

Enygma6

Additional testing, and I still can't tell for sure how or when Bone Dragon will return to the battlefield when killed.
This was the last match that I ran (all kill spells on my turn were targeting my own Bone Dragon):
Turn 9: use Fill the Graves (FtG);
cast Bone Dragon;
cast To the Slaughter
- failed to return.

Turn 15: use FtG (2nd);
cast Bone Dragon;
cast Murder
- returned as expected

turn 17: use FtG (3rd)
turn 22: opponent cast To the Slaughter on my Bone Dragon
- returned as expected

turn 23: use FtG (4th)
turn 25: use FtG (5th);
cast Murder
- returned as expected

turn 27: use FtG (6th);
cast Unholy Hunger
- failed to return

So that's 2 failures and 3 successes on the resurrection ability of Bone Dragon in one fight.  
Preceding each kill, there was a recent use of Fill the Graves, sometimes on the same turn.
No other cards from either side interacted with my graveyard.
Bone Dragon was never reinforced in this fight.

The only thing I can think of is that Bone Dragon requires more than 8 cards in the graveyard, AND it exiles the ENTIRE graveyard when it enters the battlefield.  Even when reinforced (this would fit from my experience in the 2nd post above).

Enygma6

The only thing I can think of is that Bone Dragon requires more than 8 cards in the graveyard, AND it exiles the ENTIRE graveyard when it enters the battlefield.  Even when reinforced (this would fit from my experience in the 2nd post above).

Confirmed that this is also NOT the case.  
Cast Bone Dragon on one turn, then next turn use Fill the Graves, kill the dragon with Unholy Hunger, and it does not come back.  This was already several turns in to the fight, so there were more than 8 cards in my graveyard (but it was the first use of Fill the Graves).  

At the end of the match, after having used Fill the Graves a few more times, I used 2 separate kill spells to kill the Bone Dragon twice in a row, with it returning to the battlefield both times.  One spell was Murder, the other was either To the Slaughter or Unholy Hunger (I don't recall which).

Tombstone

Thank you for passing this information along to us. I'll relay this behavior to the team for investigation. 

DBJones

I wonder if Fill the Graves messes up the graveyard count somehow, until something else interacts with the graveyard or the turn switches? Destroying Bone Dragon yourself right after using that ability seemed to be the problem in both the descriptions.

Enygma6

There were times where I used Fill the Graves and killed the Bone Dragon in the same turn, and it did return.  
The only things I can think of are:
a) a graveyard size count parameter is set at beginning of turn, so adding to it on my turn does not increment the counter that Bone Dragon checks to see if it can return.  But that doesn't make sense from a good programming perspective, nor does it account for the times in which the dragon did not return when my opponent Bolas had used his ability to kill it after I had used Fill the Graves on 3 separate turns leading up to that point.
b) kill cards with an additional effect (Unholy Hunger being the major consistent culprit in my deck above, and To the Slaughter being a sometimes effect) causing the game to lose track of the Bone Dragon on-destroy effect.  But that also does not account for the incident from the Bolas ability kill, as that has no additional effect.  
  
Hopefully the dev team can get some deeper insight into this than I am capable of.